Synthesis and antibacterial activity of silver nanoparticles with different sizes

Silver nanoparticles with different sizes (7, 29, and 89 nm mean values) were synthesized using gallic acid in an aqueous chemical reduction method. The nanoparticles were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), and ultraviolet–visible (UV–Vis) absorption spectroscopy; the antibacterial activity was assessed using the standard microdilution method, determining the minimum inhibitory concentration (MIC) according to the National Committee for Clinical Laboratory Standards. From the microscopies studies (TEM) we observed that silver nanoparticles have spherical (7 and 29 nm) and pseudospherical shape (89 nm) with a narrow size distribution. The sizes of the silver nanoparticles were controlled by varying some experimental conditions. It was found that the antibacterial activity of the nanoparticles varies when their size diminishes.     

Ultrasonic-assisted electrodeposition of Cu-Sn-TiO2 nanocomposite coatings with enhanced antibacterial activity

Copper-based coatings are known for their high antibacterial activity. In this study, nanocomposite Cu–Sn–TiO₂ coatings were obtained by electrodeposition from an oxalic acid bath additionally containing 4 g/dm³ TiO₂ with mechanical and ultrasonic agitation. Ultrasound treatment was performed at 26 kHz frequency and 32 W/dm³ power. The influence of agitation mode and the current load on the inclusion and distribution of the TiO₂ phase in the Cu–Sn metallic matrix were evaluated. Results indicated that ultrasonic agitation decreases agglomeration of TiO₂ particles and allows for the deposition of dense Cu–Sn–TiO₂ nanocomposites. It is shown that nanocomposite Cu–Sn–TiO₂ coatings formed by ultrasonic-assisted electrodeposition exhibit excellent antimicrobial properties against E. coli bacteria.     

Wettability and antibacterial activity of modified diamond-like carbon films

Diamond-like carbon (DLC) films can be used in a numerous industrial applications, including biomedical coatings with bactericidal properties. It has been demonstrated that DLC surface can be modified with oxygen plasma treatment. The purpose of this paper is to study the wettability and bactericidal activity of oxygen plasma-treated DLC films produced by plasma enhanced chemical vapor deposition technique. The sp³/sp² ratio increased after the treatment due to the increase in the generation of the unstable carbon bonds caused by the energetic ions, especially O-H group. The treated DLC surface becomes superhydrophilic and rougher, although the roughness values are still lower. DLC antibacterial activity did not increased with plasma treatment. Therefore, oxygen plasma treatment can be used to make superhydrophilic DLC but not to increase its bactericidal properties.     

The influence of ultrasound on the fluoroquinolones antibacterial activity

In this work, the antibacterial effect of fluoroquinolones (FQs) upon Escherichia coli (E.coli) was measured with and without application of 40 kHz ultrasound (US) stimulation. The research results demonstrated that simultaneous application of 40 kHz US apparently enhanced the antibacterial effectiveness of FQs. That is, the synergistic effect was observed and the bacterial viability was reduced when FQs and US were combined. In addition, various influencing factors, such as FQs drug concentration, US irradiation time and solution temperature, on the inhibition of E.coli were also investigated. The antibacterial activity was enhanced apparently with increasing of FQs drug concentration, US irradiation time and solution temperature. Furthermore, we discussed preliminarily the mechanism of US enhanced antibacterial activity. Results show that US can activate FQs to produce reactive oxygen species (ROS) indeed, which are mainly determined as superoxide radical anion (·O(2)(-)) and hydroxyl radical (·OH).     

Theoretical studies and antibacterial activity for Schiff base complexes

New ligand 4‐((2‐Hydroxy1‐naphthyl) methylene amino)‐1.5‐dimethyl‐2‐phenyl‐1H‐pyrazol‐3(2H)‐one (HL) was synthesized from the reaction of 2‐hydroxy‐1‐naphthaldehyde and 4‐aminophenaz one. A complexes of this ligand [VO(II)(HL)(SO₄)], [Pt(IV)(L)Cl₃], [Re(V)(L)Cl₃]Cl, and [M(II)(L)Cl] (M═Pd(II), Ni(II), Cu(II)) were synthesized. The resulted compounds were characterized by IR, NMR (¹H and ¹³C), mass spectrometry, element analysis, and UV‐Vis spectroscopy. Additionally, the spectroscopic studies revealed octahedral geometries for the Re(V), Pt(IV) complexes, and square pyramidal for VO(II), square planar for Pd(II) complex, and tetrahedral for the Ni(II) and Cu(II) complexes. Thermodynamic parameters (ΔE^*, ΔH^*, ΔS^*, ΔG^*, and K) were calculated using from the TGA curve Coats‐Red fern method. Therefore, hyper Chem‐8 program has been used to predict structural geometries of compounds in the gas phase. Finally, the synthesized Schiff base and its metal complexes were screened for their biological activity against bacterial species, 2 Gram‐positive bacteria (Bacillus subtilis and Staphylococcus aureus) and 2 Gram‐negative bacteria (Escherichia coli and Pseudomonas aeruginosa).     

Preliminary investigations on the antibacterial activity of zinc oxide nanostructures

We have fabricated electroactive multilayer thin films containing ferritin protein cages. The multilayer thin films were prepared on a solid substrate by the alternate electrostatic adsorption of (apo)ferritin and poly(N-isopropylacrylamide-co-2-carboxyisopropylacrylamide) (NIPAAm-co-CIPAAm) in pH 3.5 acetate buffer solution. The assembly process was monitored using a quartz crystal microbalance. The (apo)ferritin/poly(NIPAAm-co-CIPAAm) multilayer thin films were then cross-linked using a water-soluble carbodiimide, 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide. The cross-linked films were stable under a variety of conditions. The surface morphology and thickness of the multilayer thin films were characterized by atomic force microscopy, and the ferritin iron cores were observed by scanning electron microscopy to confirm the assembly mechanism. Cyclic voltammetry measurements showed different electrochemical properties for the cross-linked ferritin and apoferritin multilayer thin films, and the effect of stability of the multilayer film on its electrochemical properties was also examined. Our method for constructing multilayer films containing protein cages is expected to be useful in building more complex functional inorganic nanostructures.     

Polylactic acid (PLA)/Silver-NP/VitaminE bionanocomposite electrospun nanofibers with antibacterial and antioxidant activity

The antibacterial property of silver nanoparticles (Ag-NPs) and the antioxidant activity of Vitamin E have been combined by incorporation of these two active components within polylactic acid (PLA) nanofibers via electrospinning (PLA/Ag-NP/VitaminE nanofibers). The morphological and structural characterizations of PLA/Ag-NP/VitaminE nanofibers were performed by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy and X-ray diffraction. The average fiber diameter was 140 ± 60 nm, and the size of the Ag-NP was 2.7 ± 1.5 nm. PLA/Ag-NP/VitaminE nanofibers inhibited growth of Escherichia coli, Listeria monocytogenes and Salmonella typhymurium up to 100 %. The amount of released Ag ions from the nanofibers immersed in aqueous solution was determined by Inductively Coupled Plasma Mass Spectrometry, and it has been observed that the release of Ag ions was kept approximately constant after 10 days of immersion. The antioxidant activity of PLA/Ag-NP/VitaminE nanofibers was evaluated according to DPPH (2,2-diphenyl-1-picrylhydrazyl) method and determined as 94 %. The results of the tests on fresh apple and apple juice indicated that the PLA/Ag/VitaminE nanofiber membrane actively reduced the polyphenol oxidase activity. The multifunctional electrospun PLA nanofibers incorporating Ag-NP and Vitamin E may be quite applicable in food packaging due to the extremely large surface area of nanofibers along with antibacterial and antioxidant activities. These materials could find application in food industry as a potential preservative packaging for fruits and juices.     

Chitosan-Zinc Oxide hybrid composite for enhanced dye degradation and antibacterial activity

In this report, chitosan (CS) encapsulated zinc oxide (ZnO) hybrid composite was prepared by chemical precipitation method. The CS-ZnO composite was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis (TGA), transmission electron microscopy, and zeta potential. The composite exhibited high photocatalytic activity as evident from the degradation of methylene blue dye under UV irradiation. Approximately, 64% of the dye was degraded under UV irradiation within 3?h. In addition, the CS-ZnO composite showed excellent antibacterial activity against Escherichia coli as measured by colony forming units. Based on the data of present investigation, the composite being a biocompatible, eco-friendly, and low-cost material could find potential applications in various fields.     

Investigation into the antibacterial activity of monodisperse BSA-conjugated zinc oxide nanoparticles

The antibacterial behavior of bovine serum albumin conjugated zinc oxide nanoparticles against Escherichia coli was investigated. The zinc oxide nanoparticles were synthesized by using bovine serum albumin as the structure directing agent. And the morphology and crystal phase of the zinc oxide nanoparticles were determined by transmission electron microscopy, X-ray diffractograms and Fourier transform infrared spectrograph techniques. The synthesized zinc oxide nanoparticles showed high antibacterial activity when compared with plain zinc oxide. And the antibacterial activity was assessed by measuring the growth inhibition and testing the zone of inhibition. Furthermore, the plausible mechanism of antibacterial behavior was attributed to the generation of reactive oxygen species by zinc oxide nanoparticles.     

Preparation of sonoactivated TiO2-DVDMS nanocomposite for enhanced antibacterial activity

Titanium dioxide (TiO₂) nanoparticle has good photo-/sono-catalytic features, the reunion of this particle in solution-phase generally limits the extensive biomedical application. In the present study, the aggregation of TiO₂ nanoparticles was alleviated by facile fabrication under different pH conditions. A novel TiO₂ nanocomposite was further synthesized by properly conjugation with trace amount of DVDMS sensitizer (named DFT). The characterization, sonoactivity, as well as the antibacterial efficiency were specially evaluated. The results showed that the sonochemical activity of DFT was greatly improved as compared with the simple surface modification of TiO₂ (F-TiO₂) and free DVDMS, regarding to the hydroxyl radicals and singlet oxygen yields using the same ultrasound exposure. Moreover, ultrasonic stimulation of DFT exhibited excellent bacterial eradication, with up to 92.41% of killing efficiency in S. aureus. The flow cytometry analysis indicated an increased intracellular ROS and membrane disturbance by combination of DFT and ultrasound. The findings suggest that the proper fabrication and DVDMS incorporation greatly improved the sonocatalytic process of TiO₂, and the ultrasound based biomedical applications of DFT deserve future deep investigation.     

Synthesis and characterization of polyester bionanocomposite membrane with ultrasonic irradiation process for gas permeation and antibacterial activity

Optically active bionanocomposite membranes composed of polyester (PE) and cellulose/silica bionanocomposite (BNCs) prepared with simple, green and inexpensive ultrasonic irradiation process. It is a novel method to enhance the gas separation performance. The novel optically active diol containing functional trifluoromethyl groups was prepared in four steps reaction and it was fully characterized by different techniques. Commercially available silica nanoparticles were modified with biodegradable nanocellulose through ultrasonic irradiation technique. Transmission electron microscopy (TEM) analyses showed that the cellulose/silica composites were well dispersed in the polymer matrix on a nanometer scale. The mechanical properties nanocomposite films were improved by the addition of cellulose/silica. Thermo gravimetric analysis (TGA) data indicated an increase thermal stability of the PE/BNCs in compared to the pure polymer. The results obtained from gas permeation experiments showed that adding cellulose/silica to the PE membrane structure increased the permeability of the membranes. The increase in the permeability of the gases was as follows: P_CH4 (38%) <P_N2 (58%) <P_CO2 (88%) <P_O2 (98%) Adding silica nanoparticles into the PE matrix, improved the separation performance of carbon dioxide/methane and carbon dioxide/nitrogen gases. Increasing the cellulose/silica mass fraction in the membrane increased the diffusion coefficients of gases considered in the current study. Further, antimicrobial test against pathogenic bacteria was carried out.     

Synthesis,spectral studies,and catalytic and antibacterial activity of Ru(II) complexes with coordinated amides

Twelve Ru(II) complexes with coordinated amides were synthesized and characterized by elemental, IR, ¹H, ¹³C, ³¹P NMR, mass, and electronic spectral analysis, along with magnetic and conductance measurements. Molecular formulas and octahedral structures have been tentatively proposed. These complexes were used as catalysts for the hydrolysis of rivastigmine and neostigmine. The hydrolyzed products were coupled with 3-methyl benzothiazolinone hydrazone reagent in the presence of sodium metaperiodate and the resulting colored products were determined spectrophotometrically. The yields of hydrolyzed products were found to be 98.47% and 99.75% respectively. All the ligands and Ru(II) complexes were screened for antibacterial activity. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 867–874, November–December, 2008.     

One-pot green fabrication and antibacterial activity of thermally stable corn-like CNC/Ag nanocomposites

Corn-like cellulose nanocrystals/silver (CNC/Ag) nanocomposites were prepared by formic acid/hydrochloric acid hydrolysis of commercial microcrystalline cellulose (MCC), and redox reaction with silver ammonia aqueous solution (Ag(NH₃)₂(OH)) in one-pot green synthesis, in which the preparation and modification of CNCs were performed simultaneously and the resultant modified CNCs could be as reducing, stabilizing and supporting agents for silver nanoparticles. The influences of the Ag⁺ ion concentrations on the morphology, microstructure, and properties of the CNC/Ag nanocomposites were investigated. It is found that corn-like CNC/Ag nanocomposites containing Ag nanoparticles with diameter of about 20–40 nm were obtained. Compared to the MCCs, high crystallinity of 88.5 % and the maximum degradation temperature (T _max) of 364.5 °C can be achieved. Moreover, the CNC/Ag nanocomposites showed strong antibacterial activity against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Furthermore, such nanocomposites can act as bifunctional nanofillers to improve thermal stability, mechanical property, and antibacterial activity of commercial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(lactic acid).     

Fabrication and characterization chitosan/functionalized zinc oxide bionanocomposites and study of their antibacterial activity

This study deals with preparation and evaluation of properties of chitosan/zinc oxide bionanocomposites (CT/ZnO BNCs) with different amounts of modified zinc oxide nanoparticles (ZnO NPs) through ultrasonic irradiation technique. Due to the high surface energy and tendency for agglomeration, the surface ZnO NPs was modified by a coupling agent as 3-aminopropyltriethoxysilane (APS) to form APS–ZnO nanoparticles. Fourier transform infrared (FTIR) spectroscopy confirmed that APS was successfully grafted onto the ZnO nanoparticles surface. Thermogravimetric analysis (TGA) revealed a surface coverage of the coupling molecule of 2.6 wt%. The resulting bionanocomposites were characterized by FTIR spectra, X-ray diffraction patterns, and TGA. The antibacterial activity of bionanocomposite films was tested against gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). The results of CT/ZnO BNCs revealed that the thermal and antibacterial properties obviously improved the presence of ZnO NPs in comparison with the pure CT and that this increase is higher when the NP content increases. Further, it was observed that antibacterial activity of the resulting hybrid biofilms showed somewhat higher for gram-positive bacteria compared to gram-negative bacteria.     

Shape-controlled synthesis of Cu2O nano/microcrystals and their antibacterial activity

Uniform cuprous oxides with different morphologies have been successfully synthesized using polyvinylpyrrolidone (PVP) as a capping agent. X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis spectrophotometer, Fourier transform infrared spectrometer (FTIR) and X-ray photoelectron spectroscopy were employed to characterize the structure and morphology of cuprous oxides. It was found that the reaction conditions such as PVP, reducing agent and complexing agent played important roles in the formation of regular cuprous oxide crystals. In addition, their antibacterial activity against Bacillus subtilis (B. subtilis), Staphylococcus aureus (S. aureus), Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa) was also investigated by the Oxford cup method. Results suggested that cuprous oxides are selective in their antibacterial action. They display effective antibacterial activity against S. aureus, B. subtilis and P. aeruginosa. There is no bactericidal ability against E. coli in the tested concentration range, which indicates that E. coli may be a Cu(I)-tolerant bacterium.     

Mixing thiols on the surface of silver nanoparticles: preserving antibacterial properties while introducing SERS activity

The purpose of the study was to prepare and characterize nanosuspensions that can maintain high and extended supersaturation to improve the dissolution and absorption of poorly soluble 10-hydroxycamptothecin (10-HCPT). 10-HCPT oral nanosuspensions (HCPT-Nanosuspensions) were produced on a laboratory-scale by microprecipitation- high pressure homogenization method. The particle morphology and the physical state were studied using transmission electron microscopy, X-ray powder diffraction (XRPD), and differential scanning calorimetry (DSC). Supersaturated dissolution tests were carried out with the paddle method. Caco-2 cell experiments were performed to imitate the oral absorption. The in vivo pharmacokinetics studies were undertaken in rats following oral administration. The 10-HCPT nanoparticles were 135 nm in dimension before lyophilization and were claviform or lump in shape. XRPD and DSC both confirmed that a portion of 10-HCPT was present in a crystalline state in nanosuspension. Supersaturated dissolution tests showed HCPT-Nanosuspensions could maintain high supersaturated level for an extended period time. The cell experiment on HCPT-Nanosuspensions showed a significantly higher uptake and greater membrane permeability compared with the other formulations. The pharmacokinetic test exhibited HCPT-Nanosuspensions had a similar pharmacokinetic performance with 10-HCPT solution. In conclusion, highly and extendedly supersaturated HCPT-Nanosuspensions have been prepared which could result in high peak concentration (C _max) and great exposure (AUC) after oral administration.

     

Synthesis, spectroscopy and antibacterial activity of supermolecular compounds of organotitanium substituted heteropolytungstates containing 8-quinolinol

Parent compounds of cyclopentadienyltitanium substituted heteropolytungstates with Keggin structure, An[(CpTi)XW11O39]· xH2O (A=Me4N, K; X=P, Si, Co; Cp=η5-C5H5) were synthesized in　aqueous phase. By allowing parent heteropoly compounds to react with protonated 8-quinolinol, he title　supermolecular compounds (C9H8NO)mAn[(CpTi)XW11O39] · xH2O (A=Me4N, H; X=P, Si, Co) were synthesized. The title compounds were characterized by means of elementary analysis, IR, UV, 1H NMR,XRD and TCG-DSC. The results indicate that the title compounds are new heteropoly compounds, and there is a charge transfer interaction between the organic cation and heteropoly anion. The results obtained from thermal analysis show that QCpTiPW, QCpTiSiW and QCpTiCoW begin to decompose at 212.4, 194. 2 and 171.2℃, respectively. The results obtained from antibacterial test reveal that QCpTiSiW has the best antibacterial activity, and the MIC values of QCpTiSiW against Escherichia coli and Staphylococcus aurous are 64. 0 and 0. 500 μg · mL-1 , respectively.